Attrition of new chemical entities at late preclinical and clinical stages of development is an extremely costly event, most commonly associated with the detection of unexpected arrhythmogenic properties in novel drugs. Undetected arrhythmia-inducing effects are also the most common reason for drug withdrawal from the market. To this end, the FDA now mandates that all new drugs be tested for potential arrhythmogenic properties, which has led to a growing market for accurate and cost effective preclinical screening tools. Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) represent the means to generate superior in vitro cardiac tissues for such applications. However, an inability for hPSC-CMs to develop into adequate representations of adult myocardial tissue is a major impediment to the use of these cell-constructs in effective preclinical screening protocols. Generation of mature cardiac tissues that accurately recapitulate the form and function of the adult human myocardium is necessary to provide preclinical data capable of reliably predicting a compound's efficacy and/or toxicity when transferred to a clinical setting. This proposal focuses on the development of a nanopatterned microelectrode array (MEA) platform with which to evaluate the arrhythmogenic potential of novel compounds in a high throughput and predictive manner. Nanotopographic surfaces are known to promote the maturation of cultured hPSC-CMs towards phenotypes representative of the adult human myocardium. We hypothesize that the integration of such topographic signaling cues with MEAs will enable the analysis of the electrophysiological performance of these matured human cardiomyocytes in vitro. Furthermore, we posit that the topography-mediated maturation of hPSC-CMs will lead to the generation of cardiac monolayers with electrophysiological properties more closely representative of adult cardiac tissue in terms of conduction velocity, anisotropic conduction patterns, and field potential durations. Finally, we suggest that the establishment of this mature functional assay will enable the collection of compound arrhythmogenesis data with greater predictive capacity in terms of recreating in vivo drug effects in vitro. To test these hypotheses, this grant will focus n the design and production (Task 1) of topographically patterned multiwell MEAs. The ability for hPSC-CMs cultured within this platform to generate drug-induced arrhythmia data for known arrhythmogenic compounds that are representative of these drugs' activity in vivo will then be investigated (Task 2). Comparison of compound action on nanopatterned and flat cardiomyocyte monolayers to drug activity in vivo will be used to demonstrate the improvement our platform offers in terms of predicting myocardial responses to drug treatment. Successful validation of this nanopatterned MEA system will produce a new product for advancing the efficacy of preclinical drug screening with the potential to streamline current pharmaceutical development. This system, for which we own the Intellectual Property, will be of considerable interest to both academic and pharmaceutical screening laboratories, and we will seek to commercialize our prototype upon successful completion of this grant.